====== Description of the variables ======

For each car driver we observe the following quantities, measured over a certain time window of mobile activity:  

  Length = total traveled distance (m.)
  Duration = total time spent driving (sec.)
  Count = number of different trips
  Phighway = distance traveled on highways (m.)
  Pcity = distance traveled inside cities (m.)
  Length_arc_crowded = distance traveled on 20% most crowded roads (m.)
  Pnight = distance traveled at night time (m.)
  Pover = distance traveled over speed limit (m.)
  Profile = number of systematic trips, e.g., work-home
  Radius_g = radius of gyration: sparsity of location from the center of mass of the driver (mean position)
  Radius_g_L1 = radius of gyration w.r.t. L1: sparsity of location from the driver's most frequent location (e.g., home)
  Avg_Dist_L1 = average distance from L1:  average distance from the driver's most frequent location (e.g., home)
  TimeL1L2 = % time spent at locations L1 and L2 (most and second most preferred locations)
  EntropyArc = entropy on road segment frequencies, measures the diversity of roads traveled
  EntropyLocation = entropy on location frequencies, measures the diversity of places visited
  EntropyTime = entropy on hours of the day, measures the diversity of daily patterns

Notice that there are no missing values in the dataset, hence "0"s are actual "0"s, NOT missing values.